The present invention relates generally to a metals recovery system. More specifically, the present invention relates to the methods and apparatus for recovery of metals from mined ore.
In heap leach mining operations, ore (pieces of mineral, rock, or soil that also bear a valuable metal) is placed on a containment liner system (also known as a heap leach pad) and continuously sprayed or irrigated with a process fluid to wet the entire ore heap. The process fluid extracts metals in the ore upon contact with the ore and carries the metal away in solution as the solution infiltrates through the ore heap. Process fluid carrying extracted metal is known as pregnant solution. The pregnant solution that infiltrates through the ore heap is collected at the bottom of the ore heap and transported to processing equipment for separating the metal and the process fluid.
As process fluid infiltrates through the ore heap, preferred flow channels or pathways may begin to form within the ore heap. Such preferred flow paths result in other areas of the ore heap no longer being contacted with process fluid that can carry away extracted or dissolved metals. Ore that has previously been wetted with process fluid but is not located along a preferred flow path will decrease in moisture content, below the ore material's field capacity, to the extent that free solution containing dissolved metal will no longer mobilize through the ore, leaving dissolved metal within the pore spaces of variable sized pieces of ore, adhered to the surface of the ore and/or absorbed within more porous or absorbent ore types. Furthermore, at the end of mining operations these heaps are drained down and a moisture content at approximately the field capacity of the various ore types within the heap will remain within the previously wetted ore material “trapping” dissolved metal in the heap. Due to the lack of a cost-effective method of removing this “trapped” metal, it usually remains within the heap at the close of mining operations and is considered “lost.”